Pulse-width modulation (PWM) is a technique for controlling analog circuits with digital outputs of a microprocessor or with a discrete modulator. PWM is employed in a wide variety of applications, ranging from measurement and communications to power control and conversion.
PWM is used in the common “switch-mode” power supplies that convert AC power to DC for computers and other electronic devices. It can be used to control the speed of a DC motor, the brightness of a light bulb, or an output of audio amplifiers. Due to the discrete nature of the PWM output, PWM amplifiers may produce less heat than traditional analog amplifiers.
Pulse-width modulation of a signal or power source involves the modulation of its duty cycle to either convey information over a communication channel or control the amount of power sent to some loads. High-frequency perturbations from a carrier frequency used in the PWM and its harmonics may interfere with the recovery of information from the pulse-width modulated signal.